Thermal properties and spectroscopic properties of the glass micro-sphere were presented in this paper. The Er3+ emission
spectra of a kind of Erbium-doped glass microsphere were measured and discussed under 532nm excitation in a series of
temperatures. The change in the temperature of the microsphere leads to a change in both the size and the index of
refraction of the sphere, which results in the resonance shift of the peaks of whispering gallery modes in emission spectra.
The temperature of the environment surrounding the sphere can be determined by monitoring the shift, which allows us to
calibrate the sensing function of the shift proportional to temperature. Based on the thermal effects, we propose a novel
optical temperature sensor using micrometer-sized sphere.